What if travel is fatal to optimism and open-mindedness? I don't see how cultural exchange necessarily leads to more acceptance. For the pessimist, it reinforces a belief in a "malevolently useless" human condition insofar as suffering, and the inadequate answers to suffering, are universal. The failed optimist is driven by a belief in a terra incognita with no discrimination, no hostility between the identities we adopt etc. - yet he finds none. The world is mapped out for him and slowly but surely, every image of a concrete sanctuary turns out to be ridiculous and infantile. Think Roquentin in Nausea.
You have to be careful with historical analogies for both theoretical and practical reasons. Every time you cite Hellenism or whatever to support your claim, you better expect a plethora of counter-analogies ranging from the Roman Empire to the cultural climate of Weimar.
You mean if you go looking for shangrila you may not find it or that for every citation there can be a dozen others?
Pretty pessimistic wouldnt you say?
You may not find what you are looking for if you travel but you're sure to find something and I'm betting its something different to what you know.
Now, I'd say sure that if you are a western liberal protest warrior you could find that things are worse than they are at home, easily, that's what Peter Thatchell found when he went to Russia behaved as he often does at home pushing around elderly religious figures and to his surprise a skinhead broke his nose.
I would guess that most people would not be so naive and there has been lots of coverage of the cases of westerners who have had trouble with laws governing the casual transport of bottles of beer in their cars, ladies sun bathing, all those major cultural interface issues.
Personally, I dont think that travel should make the case for either pessimism or optimism, whatever your bias is will determine that in any case. Whether you travel or not. Although, it does make you realise that a whole other world exists which is nothing like the one you live in, coming from NI and disliking many of the aspects of the tribalism here I loved going places were it made no sense what so ever as it did not exist. Its highly unique in its toxicity and when I've seen alt right types try to integrate it with their White Anglo-Saxon Protestant ideology its still not a perfect fit.
So far as history goes, I'm a socialist, there's lots of experience of projecting hopes on to history, whether its the linear "progressivism" of liberalism, which a lot of socialists inherited, or Marx's Hegelian historical materialism of thesis, anti-thesis, synthesis and new thesis arriving in the shape of class struggles and Marx's idea that communism was the riddle of history solved. So, yeah. Popper was probably right when he decried the poverty of historicism.
Even in an individual or family history there's nothing to say that lessons and insights follow on experience and events, so there's nothing to suggest that history automatically results in improvement on the micro, let alone macro level.
That's before you get into the pretty relentless revisionism and attempts to erase memory and history which is largely the greater part of liberalism. That's positively self-sabotage but because conservatism is so hateful, so hateful to the majority of people who live in the moment and are told anything is possible if you want it enough, the actual part of it that ought to make sense isnt going to go over well.